What’s Not in This Book

This is not an introduction to JavaScript. If you’re new to the language, or if you just want a refresher, I highly recommend Kyle Simpson’s excellent You Don’t Know JS^[2] series. Most of the code in this book will employ features added to the language as part of the ECMAScript 6 (also known as ES6 or ES2015) standard. Here’s a quick test:

If any of that syntax is confounding, you’ll find clarity in the ES6 & Beyond volume of Simpson’s book series.

Some familiarity with React is helpful, but not required. I’ll give a brief explanation for each React concept we encounter. If you want a more thorough introduction, pick up Ludovico Fischer’s React for Real.^[3]

All tests in this book are unit tests, meaning the JavaScript code is tested in isolation. We won’t be covering integration tests (e.g., a test where the JavaScript code talks to a database) or functional tests (e.g., a test where a tool like Selenium interacts with the code as it runs in a browser). While I don’t quite believe that such tests are a scam,^[4] the fact is that they require far more effort to implement, run, and maintain than unit tests. My advice is to achieve a high degree of code coverage with unit tests first, then add more layers of testing as needed.